Owing to the technological developments and trends, portable products tend to be smaller and lighter. For example, mobile phones, notebook computers, camcorders, or personal digital assistants (PDAs) adopt the design concept towards lightness, thinness, shortness, and smallness. Thereby, batteries for the portable products have to be miniaturized. Due to miniaturization of the batteries, the capacity thereof is reduced. Hence, the usage time of the portable products is shortened accordingly. When using notebooks computers, mobile phones, or camcorders, low battery condition happens frequently owing to low capacity of the batteries. Besides, charging takes time, and carrying the charger is troublesome. When going abroad, it is possible that the plug specification of the charger is not compatible with the outlet.
If a portable product can free a user from the charging problems and can make the user use the portable product anytime and anywhere, its convenience will definitely enhance. However, the capacity of current lithium batteries has approached theoretical limits, thus they are difficult to meet the power demand of future portable products. With diversification in functions of portable products, the power demand increases rapidly. Thereby, it is needed urgently a novel battery, which not only can maintain the design concept of miniaturization, but also can sustain long-time usage. A fuel cell has the characteristic of high energy density. Once the fuel (such as hydrogen or methanol) is supplied continuously, power can be generated uninterruptedly. Accordingly, people are interested in the application of fuel cells in power supply and backup power.
Nevertheless, the voltage of a single fuel cell is relatively low. Depending on different characteristics of fuels, the theoretical voltage of the electrochemical cells is around 1 volt, which is not applicable to electronic precuts. Thereby, multiple cells will generally be cascaded to form a battery set with suitable voltage and capacity.
FIG. 1 shows a structural schematic diagram of stacked fuel cells according to the prior art. As shown in the figure, the general cascading method is to stack the cells, and use a bipolar plate 5 as a connector to form a fuel cell stack 10. Adopting the bipolar plate 5 is more efficient, because the bipolar plate 5 itself is like a wire to connect the positive and the negative terminals, thus avoiding possible impedance increase due to wiring, and saving the volume and weight of an electrode plate.
FIGS. 2A and 2B show a side view and top view of planar fuel cells according to the prior art. As shown in the figures, planar arrangement is adopted by the prior art, and wires are used to cascade the independent single cells 15. However, in some application environments, owing to limitation imposed by space and geometry, independent single cells 15 can only be arranged planarly. Take the structure of a notebook computer for example. Because the appearance of the product is flat, stacked batteries cannot be integrated into the machine like lithium-ion batteries, but can only be connected externally and used as a backup power, which does not comply with the usage behavior of normal customers. Thereby, planar fuel cells with cascade connection are obviously an inevitable design direction in notebook computer application. This is also true for other consumer electronic products.
FIG. 3 shows a three-dimensional view of planar fuel cells according to another prior art. As shown in the figure, the current common method of cascading planar fuel cells is to secure a plurality of single cells 25 on a substrate 30. However, because the fuel is inputted from the top of the substrate 30, and the oxidant gas is inputted from the bottom of the substrate 30, thus it is convenient for the connection of the fuel pipes and oxidant gas pipes. That is to say, the negative terminals of all single cells 25 are on the top, while the positive terminals are at the bottom. Hence, when cascading a plurality of single cells 25, the wires have to be connected in the fashion of one end on the top and the other at the bottom, which makes wiring complex. In addition to complex electrical wiring, the supply of the fuel and oxidant gas is also troublesome, especially the connection of the liquid and gas pipes. Without excellent design of joints, leakage tends to occur.
Accordingly, the present invention provides a coupling structure of fuel cells, which cascades the fuel cells planarly, and simplifies wiring problems while cascading the fuel cells. Besides, the fuel and oxidant gas can be supplied conveniently. Thereby, the problems occurred in the prior art as described above can be solved.